This invention relates to an image processing apparatus such as a digital copying machine which forms an image on a recording sheet on the basis of image data obtained from image input means.
Conventionally, a digital copying machine is proposed in which image data are stored into storage means and a recording process is performed using image data read out from the storage means, so that the period required for obtaining a predetermined number of copy sets are shortened and the productivity is improved (Japanese Patent Unexamined Publication No. Hei. 2-81563).
More specifically, as shown in FIG. 11, control means 54 controls the copying process as follows. Image data for a first copy set of an original fed by automatic document feed means 50 are sequentially read by original read means 51. The obtained image data are recorded by image record means 53, and simultaneously stored into image storage means 52. The process of recording second and subsequent copy sets is performed using image data read out from the image storage means 52. Since copy sets are obtained on the basis of stored image data in this way, the copying process can be performed at a high speed irrespective of the speed of reading image data from the original, thereby shortening the period required for obtaining a predetermined number of copy sets.
Such a conventional copying machine has the following problems:
(1) The use of a semiconductor memory as the image storage means allows random access to be quickly done. In the case that two or more copy sets of an original of job 1 are to be obtained, therefore, image data of an original of job 2 can be relatively easily read while performing a process of recording second and subsequent copy sets. When a semiconductor memory of a large capacity is used as the image storage means, however, the cost of the storage means is much higher than that of storage means composed of a storage device of another type.
(2) Although the use of an optical disk, a magnetic disk or a floppy disk as the image storage means reduces its cost, such a storage device operates slowly so that it is difficult to read image data of an original of job 2 while performing a process of recording second and subsequent copy sets of job 1. Therefore, image input means cannot perform the image input process and must remain in a wait status, until the output of second and subsequent copy sets of job 1 is completed.